This invention relates generally to apparatus used in conjunction with fire detection and alarm systems. More particularly it relates to the field of optical smoke detectors designed to detect an annunciate the presence of smoke in the air in or moving through the device. To increase the sensitivity of the device the components of this device are arranged so that light is efficiently collected by means of a spherical reflector.
Typical photoelectric smoke detector configurations collect only a small fraction of the smoke-scattered light. This invention collects all of the light scattered through small angles in both the forward scatter and backward scatter by means of a spherical reflector. Small angle forward and backward scattering are the predominant scattering modes for particles in the size range of interest for smoke detection.